A conventional driving assistance system for vehicle learns time to contact at the start of deceleration when the vehicle is approaching a leading vehicle ahead and generates an alarm based on a learnt value (see, for example, patent reference literature 1). The system estimates a predicted time of the driver from the time to contact at the start of deceleration operation and generates an alarm when the predicted value of the vehicle separation after the predicted time becomes smaller than an alarm distance.
Patent Reference Literature 1    Japanese Laid Open Patent Publication No. H7-159525
Patent Reference Literature 2    Japanese Laid Open Patent Publication No. 2005-71184